The answer is to update the commit hash or use a version tag pointing to the latest, then rebuild the Docker image with the --no-cache flag. This is necessary because when a Docker image is built, pip installs the package from the Git repository at the specific commit hash listed in the requirements file, and Docker’s layer caching can reuse an old cached layer containing the previous version of the package, even if the requirements file appears updated. Simply restarting the container does not rebuild the image, so the old installed package persists. On the PCAP exam, this scenario tests your understanding of how pip editable packages interact with Docker’s build cache, a common trap where candidates assume restarting a container refreshes dependencies. Remember the key distinction: container restarts do not rebuild images; only a fresh build with --no-cache forces pip to re-fetch the latest code from Git. Memory tip: “Cache is the culprit—no-cache is the cure.”
PCAP Modules and Packages Practice Question
This PCAP practice question tests your understanding of modules and packages. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are a DevOps engineer managing a Python application that consists of multiple microservices. One microservice, 'data_processor', imports a shared library 'common_lib' which is also used by other microservices. The shared library is developed in a separate repository and is installed via pip in each microservice's virtual environment as an editable package (pip install -e). Recently, you updated 'common_lib' with new functions, but when you redeploy 'data_processor' (by restarting the container), the new functions are not available; the old version is still used. The container uses a Docker image built from a requirements file that specifies 'common_lib' from a Git repository. You verify that the Git commit hash in the requirements file points to the latest version. What is the most likely cause and what is the correct course of action?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Update the commit hash or use a version tag that points to the latest, and rebuild the Docker image without using cache (--no-cache).
When a Docker image is built, pip installs the package from the Git repository at the commit hash specified in the requirements file. Even if the requirements file points to the latest commit, Docker's layer caching may reuse a previously built layer that contains the old version of the package. Rebuilding the image with --no-cache forces Docker to re-execute the pip install step, fetching the latest code from Git and installing the updated common_lib. Simply restarting the container does not rebuild the image, so the old installed package persists.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Add the common_lib source directory to sys.path in the microservice code.
Why it's wrong here
Would not help because the package is already installed; it's the version that's outdated.
✗
Rename the package in the requirements file to force a fresh install.
Why it's wrong here
Renaming is unnecessary and creates confusion.
✓
Update the commit hash or use a version tag that points to the latest, and rebuild the Docker image without using cache (--no-cache).
Why this is correct
Ensures pip installs the latest version of common_lib.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change the Python interpreter to a different version.
Why it's wrong here
Not relevant to the issue.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the misconception that restarting a container or redeploying without rebuilding the image will pick up changes from a Git-based pip dependency, when in fact the package is frozen in the image layer until the image is rebuilt with a fresh pip install.
Trap categories for this question
Similar concept trap
Renaming is unnecessary and creates confusion.
Detailed technical explanation
How to think about this question
Docker build layers are cached based on the Dockerfile instructions and the content of files copied into the build context. If the requirements.txt file content (including the commit hash) has not changed, Docker may reuse the cached layer from a previous build where pip install was executed, even if the remote Git repository has new commits. Using --no-cache ensures that every instruction is re-executed, forcing pip to fetch the latest code from the Git URL. In CI/CD pipelines, it is common to use a version tag or a dynamic commit hash in the requirements file to avoid this caching issue.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Modules and Packages — This question tests Modules and Packages — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Update the commit hash or use a version tag that points to the latest, and rebuild the Docker image without using cache (--no-cache). — When a Docker image is built, pip installs the package from the Git repository at the commit hash specified in the requirements file. Even if the requirements file points to the latest commit, Docker's layer caching may reuse a previously built layer that contains the old version of the package. Rebuilding the image with --no-cache forces Docker to re-execute the pip install step, fetching the latest code from Git and installing the updated common_lib. Simply restarting the container does not rebuild the image, so the old installed package persists.
What should I do if I get this PCAP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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